Highly Transparent and Colorless Nanocellulose/Polyimide Substrates with Enhanced Thermal and Mechanical Properties for Flexible OLED Displays

Abstract

Flexible organic light‐emitting diode (OLED) displays have attracted worldwide attention and colorless polyimides (CPIs) are their key substrate materials. However, desirable CPIs are difficult to obtain since the thermal and mechanical properties are sacrificed during CPI production through modification of colored polyimide. Here, a cellulose nanocrystal (CNC)/CPI hybrid substrate with high optical, mechanical, and thermal properties is introduced. Due to the outstanding mechanical and thermal properties of CNCs as well as their strong interfacial interaction with CPI matrix, the sacrificed properties are made up and hybrid substrate is demonstrated strikingly improved thermal properties and mechanical properties with thermal decomposition temperature of 555 °C, upper operating temperature of 320 °C, glass transition temperature of 289 °C, coefficient of thermal expansion of 31.62 ppm K−1, tensile strength of 128 MPa, elastic modulus of 3.72 GPa, and folding capacity of 160 000 times. Particularly, the substrate keeps an excellent transmittance of 86% at 600 nm and it is colorless. The OLED devices built on the hybrid substrates show outstanding performance, which is superior to that of OLED@CPI, and comparable to that of OLED@glass. It is expected that this work will open new avenues for fabricating high‐performance and low‐cost flexible OLED devices.

Evaluation in Cellulose Nanocrystals Effectiveness on Composite Film based Wound Dressing from Poly(vinyl alcohol) and Gum Tragacanth

“…The PVA/GT/CNC10 lm recorded the lowest transmittance of 46.28 ± 0.54%. High signi cant difference (p < 0.05) was recorded between PVA, PVA/GT and PVA/GT/CNC composite lms due to differences in light dispersion caused by the disparate viscosities of GT and PVA (Silva et al, 2016) and aggregation of CNCs as the concentration increased (Chen et al, 2020). Optical properties also related the re-arrangements in the internal structure of PVA molecules during the drying process (Silva et al, 2016;Tonyali et al, 2018).…”

Flexible organic optoelectronic devices on paper

“…As shown in Figure 2 B, Chen et al. prepared a CNC/colorless polyimides (CPI) hybrid substrate with high optical, mechanical, and thermal properties ( Chen et al., 2020 ). CNC has an excellence performance, with the thermal decomposition temperature of 555°C and folding capacity of 160,000 times.…”

“… (B) Schematic illustration of the preparation of cellulose nanocrystal and colorless polyimide (CNC/CPI) hybrid substrate and its application in OLED fabrication. Adapted with permission from ( Chen et al., 2020 ).Copyright 2020, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. (C) Schematic illustration of the preparation of cellulose nanofibrils and polyarylate (CNF/PAR) hybrid substrate.…”

“…Purandare fabricated OLEDs on flexible and transparent reconstituted cellulose obtained from wood pulp ( Purandare et al., 2014 ). The HOMO/LUMO energy levels and device structure of OLED are shown in Figure 9 D. The CNC/CPI hybrid substrate with high optical, mechanical, and thermal properties was applied as OLED substrate by Tao’s group ( Chen et al., 2020 ). The nanopaper-based OLED adopted a conventional bottom-emitting OLED since the high transmittance (>85%) of the CNC/CPI hybrid substrate.…”

Mechanically Strong and Tailorable Polyimide Aerogels Prepared with Novel Silicone Polymer Crosslinkers

“…Over the past few decades, aerogels made from polymer have been developed, such as phenol-formaldehyde resin [ 10 ], polyurethanes [ 11 ], polyureas [ 12 ], polyamides [ 13 ], and polyimide [ 14 ]. Compared to other aerogels, PI aerogels attracted more attention from researchers due to perfect chemical stability [ 15 ], good mechanical properties [ 16 ], perfect dielectric performance [ 17 , 18 ] and high decomposition temperatures [ 19 , 20 ].…”